Acetylation and phosphorylation of SRSF2 control cell fate decision in response to cisplatin

Abstract

SRSF2 is a serine/arginine-rich protein belonging to the family of SR proteins that are crucial regulators of constitutive and alternative pre-mRNA splicing. Although it is well known that phosphorylation inside RS domain controls activity of SR proteins, other post-translational modifications regulating SRSF2 functions have not been described to date. In this study, we provide the first evidence that the acetyltransferase Tip60 acetylates SRSF2 on its lysine 52 residue inside the RNA recognition motif, and promotes its proteasomal degradation. We also demonstrate that the deacetylase HDAC6 counters this acetylation and acts as a positive regulator of SRSF2 protein level. In addition, we show that Tip60 downregulates SRSF2 phosphorylation by inhibiting the nuclear translocation of both SRPK1 and SRPK2 kinases. Finally, we demonstrate that this acetylation/phosphorylation signalling network controls SRSF2 accumulation as well as caspase-8 pre-mRNA splicing in response to cisplatin and determines whether cells undergo apoptosis or G 2 /M cell cycle arrest. Taken together, these results unravel lysine acetylation as a crucial post-translational modification regulating SRSF2 protein level and activity in response to genotoxic stress.

Regulating the regulators: Serine/arginine‐rich proteins under scrutiny

“…These results suggest that PTM by lysine acetylation could be involved in the regulation of pre-mRNA processing events. In agreement, Edmond and collaborators have recently found that the SR protein SRSF2 is modified by acetylation within its RNA binding domain at K52 (39). SRSF2 acetylation levels are regulated by the opposing action of the acetyl-transferase TIP60 and the deacetylase HDAC6 such that acetylation by TIP60 reduces SRSF2 protein levels through proteasome-dependent degradation, while deacetylation by HDAC6 exerts the opposite effect.…”

The emerging role of pre-messenger RNA splicing in stress responses: Sending alternative messages and silent messengers

“…52 In the context of genotoxic stress, cisplatin treatment decreases TIP60-dependent acetylation and increases SRPK2-dependent phosphorylation of SRSF2 (also called SC35). 22 Interestingly, many targets of ATM/ATR, protein kinases playing key roles in DNA damage signaling, are RNA-binding proteins including SFs. 53 Also interesting, the protein kinase AKT that promotes cell survival increases the anti-apoptotic caspase 9b isoform through phosphorylation of SRSF1 (also called ASF/SF2).…”

“…For example, SRSF2 mediates the regulation of AS events in multiple apoptosis-related genes, including caspase 8, caspase 9, Bcl-x and c-flip. 20,22 Likewise, SRSF1 controls multiple apoptosis-related AS, including those of Bcl-x, Mcl1 and caspase 9. 44 It will be interesting to identify the whole sets of AS events controlled by stress-induced modifications of these and other SFs, and to determine how different modifications of the same factor (e.g., SRSF2 regulation at the levels of transcription, AS, and protein localization, phosphorylation and acetylation in response to cisplatin) might impact on different sets of exons and/or other levels of gene expression where this factor is involved.…”

“…20,21 Cisplatin induces a pro-apoptotic splice variant of caspase 8 (CASP8) through the regulation of alternative 5' splice sites in exon 8. 20,22 Cyclophosphamide, oxaliplatin and UV favor the production of the pro-apoptotic Bcl-x S isoform and decrease the anti-apoptotic Bcl-x L isoform, through the regulation of alternative 5' splice sites in exon 2. 20,21,23 Thus, genotoxic agents induce the pro-apoptotic splice isoforms of several genes.…”

SRSF2-p95 hotspot mutation is highly associated with advanced forms of mastocytosis and mutations in epigenetic regulator genes

“…12 As such, SRSF2 mutation is thought to pre-dispose early progenitor cells to malignant selection, perhaps via its role in the acetylation/phosphorylation network and as an important regulator of DNA stability and mRNA splicing. 13 We have now sequenced for SRSF2 mutation in our cohort of mastocytosis patients, previously characterized for both KIT and TET2 mutations, 7 and have revealed a striking association between SRSF2 mutation and advanced disease types.…”